This invention relates in general to loos-leaf binders and in particular to a new and useful binder having two operationally upright binder yokes which open and close together.
The invention relates particularly to a binder mechanism for loose-leaf binders comrpising an oblong, flat support plate on which are disposed at a standardized distance from each other at least two upright, two-piece binder yokes, each formed of a fixed yoke rod and a yoke part which can be pivoted about an axis vertical in a working position. The pivotable yoke parts have at the support plate level, crank arms which are interconnected by a lengthwise movable connecting link which is disposed in the support plate so that they can be operated jointly.
In one known binder mechanism of this kind (German OS No. 28 10 844) the support plate as well as the three-piece binder yokes comprise metal parts. Each three-piece binder yoke is formed of a cylindrical, hollow rod vertically fastened to the support plate, of a tubular yoke guide also fastened vertically on the support plate and running parallel to the hollow rod, and of a movable yoke which has two parallel legs of different lengths, the shorter of which is free and connected to the longer leg by a yoke. The longer leg is guided in the yoke guide so as to be movable lengthwise and it is rotatable, the free lower end of the shorter leg being engageable with the upper end of the hollow rod. The lower ends of the longer legs of the movable yokes are each provided with a lever arm bent outwardly at right angles, a number of sttionary control slots corresponding to the number of binder yokes being provided for them in the support plate. Each control slot comprises a lower, vertical slot part and an upper horizontal slot part. A sliding rod movable relative to the support plate and having control slots running obliquely relative to the support plate plane and engaged by the lever arms is provided for the movable yokes. While all yokes can be actuated jointly by actuating the sliding rod connecting them in this known binder mechanism, the function principle of the yokes which rpovides for an axial, as well as a pivoting motion when opening and closing, and the structural design tailored to the use of metal parts require relatively many components, the correct assembly of which necessitates much labor and, therefore, high costs. In addition, due to the combined axial and rotary motions generated by slot and link guiding means, great actuating forces are required which in turn cause much wear in connection with the friction occurring thereby. Add to this that the crank arms of the movable yoke parts are kept relatively short for space saving reasons so that the accuracy of motion of these movable yoke parts and, hence, their functional reliability are deficient.